package com.wtx.chapter07;

/**
 * @description: 链表映射
 * @author: wtx
 * @createDate: 2020/5/26
 */
public class LinkedListMap<K,V> implements Map<K,V> {

    //结点
    private class Node{
        public K key;
        public V value;
        public Node next;

        public Node(K key, V value, Node next) {
            this.key = key;
            this.value = value;
            this.next = next;
        }

        public Node(K key) {
            this(key,null,null);
        }

        public Node() {
            this(null,null,null);
        }

        @Override
        public String toString() {
            return "Node{" +
                    "key=" + key +
                    ", value=" + value +
                    '}';
        }
    }

    //虚拟头结点
    private Node dummyHead;
    private int size;

    public LinkedListMap() {
        this.dummyHead = new Node();
        this.size = 0;
    }

    @Override
    public void add(K key, V value) {

        Node node = getNode(key);
        if (node==null){

            dummyHead.next = new Node(key,value,dummyHead.next);
            size++;
        }else
            node.value = value;
    }

    @Override
    public V remove(K key) {

        Node prev = dummyHead;
        while (prev.next!=null){
            if (prev.next.key.equals(key))
                break;
            prev = prev.next;
        }
        if (prev.next!=null){

            Node delNode = prev.next;
            prev.next = delNode.next;
            delNode.next = null;
            size--;
            return delNode.value;
        }
        return null;
    }

    @Override
    public boolean contains(K key) {
        return getNode(key) != null;
    }

    @Override
    public V get(K key) {

        Node node = getNode(key);
        return node==null? null: node.value;
    }

    @Override
    public void set(K key, V value) {
        Node node = getNode(key);
        if (node==null)
            throw new IllegalArgumentException(key + "do not exist");
        else
            node.value = value;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size==0;
    }

    private Node getNode(K key){

        Node cur = dummyHead.next;
        while (cur!=null){
            if (cur.key.equals(key))
                return cur;
            cur = cur.next;
        }
        return null;
    }
}
